{"api_version":"1","generated_at":"2026-08-16T08:12:37+00:00","cve":"CVE-2026-72170","urls":{"html":"https://cve.report/CVE-2026-72170","api":"https://cve.report/api/cve/CVE-2026-72170.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-72170","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-72170"},"summary":{"title":"9p: skip nlink update in cacheless mode to fix WARN_ON","description":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: skip nlink update in cacheless mode to fix WARN_ON\n\nv9fs_dec_count() unconditionally calls drop_nlink() on regular files,\neven when the inode's nlink is already zero. In cacheless mode the\nclient refetches inode metadata from the server (the source of truth)\non every operation, so by the time v9fs_remove() returns, the locally\ncached nlink may already reflect the post-unlink value:\n\n  1. Client initiates unlink, server processes it and sets nlink to 0\n  2. Client refetches inode metadata (nlink=0) before unlink returns\n  3. Client's v9fs_remove() completes successfully\n  4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0\n\nThis race is easily triggered under heavy unlink workloads, such as\nstress-ng's unlink stressor, producing the following warning:\n\n  WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8\n  Call trace:\n   drop_nlink+0x4c/0xc8\n   v9fs_remove+0x1e0/0x250 [9p]\n   v9fs_vfs_unlink+0x20/0x38 [9p]\n   vfs_unlink+0x13c/0x258\n   ...\n\nIn cacheless mode the server is authoritative and the inode is on its\nway out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count()\nentirely when neither CACHE_META nor CACHE_LOOSE is set, which both\navoids the warning and removes a class of nlink races (two concurrent\nunlinkers observing nlink > 0 and both calling drop_nlink()) that an\nnlink == 0 guard alone would only narrow rather than close.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-15 06:21:35","updated_at":"2026-08-15 06:21:35"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/8faccac11e1369adddf5d80f4a45af93f13b2e1a","name":"https://git.kernel.org/stable/c/8faccac11e1369adddf5d80f4a45af93f13b2e1a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a5a682b016ef5b5384e28f6d652d47a8f8e73d37","name":"https://git.kernel.org/stable/c/a5a682b016ef5b5384e28f6d652d47a8f8e73d37","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/de79c3f3643841b8659a71958df7cf2a66bfd409","name":"https://git.kernel.org/stable/c/de79c3f3643841b8659a71958df7cf2a66bfd409","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8d610017c992de705b304d3d727a6e3a86af6149","name":"https://git.kernel.org/stable/c/8d610017c992de705b304d3d727a6e3a86af6149","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/574aa0b4799470ac814479f1138d19efe6262255","name":"https://git.kernel.org/stable/c/574aa0b4799470ac814479f1138d19efe6262255","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-72170","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72170","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ac89b2ef9b55924bcf922251f043ba73a32d05bb a5a682b016ef5b5384e28f6d652d47a8f8e73d37 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ac89b2ef9b55924bcf922251f043ba73a32d05bb de79c3f3643841b8659a71958df7cf2a66bfd409 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ac89b2ef9b55924bcf922251f043ba73a32d05bb 8d610017c992de705b304d3d727a6e3a86af6149 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ac89b2ef9b55924bcf922251f043ba73a32d05bb 8faccac11e1369adddf5d80f4a45af93f13b2e1a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ac89b2ef9b55924bcf922251f043ba73a32d05bb 574aa0b4799470ac814479f1138d19efe6262255 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.17","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 4.17 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.145 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.97 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.40 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.5 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"72170","cve":"CVE-2026-72170","epss":"0.002090000","percentile":"0.113280000","score_date":"2026-08-15","updated_at":"2026-08-16 00:00:32"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/9p/vfs_inode.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"a5a682b016ef5b5384e28f6d652d47a8f8e73d37","status":"affected","version":"ac89b2ef9b55924bcf922251f043ba73a32d05bb","versionType":"git"},{"lessThan":"de79c3f3643841b8659a71958df7cf2a66bfd409","status":"affected","version":"ac89b2ef9b55924bcf922251f043ba73a32d05bb","versionType":"git"},{"lessThan":"8d610017c992de705b304d3d727a6e3a86af6149","status":"affected","version":"ac89b2ef9b55924bcf922251f043ba73a32d05bb","versionType":"git"},{"lessThan":"8faccac11e1369adddf5d80f4a45af93f13b2e1a","status":"affected","version":"ac89b2ef9b55924bcf922251f043ba73a32d05bb","versionType":"git"},{"lessThan":"574aa0b4799470ac814479f1138d19efe6262255","status":"affected","version":"ac89b2ef9b55924bcf922251f043ba73a32d05bb","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/9p/vfs_inode.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"4.17"},{"lessThan":"4.17","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.145","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.97","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.40","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.5","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.145","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.97","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.40","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.5","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2-rc1","versionStartIncluding":"4.17","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: skip nlink update in cacheless mode to fix WARN_ON\n\nv9fs_dec_count() unconditionally calls drop_nlink() on regular files,\neven when the inode's nlink is already zero. In cacheless mode the\nclient refetches inode metadata from the server (the source of truth)\non every operation, so by the time v9fs_remove() returns, the locally\ncached nlink may already reflect the post-unlink value:\n\n  1. Client initiates unlink, server processes it and sets nlink to 0\n  2. Client refetches inode metadata (nlink=0) before unlink returns\n  3. Client's v9fs_remove() completes successfully\n  4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0\n\nThis race is easily triggered under heavy unlink workloads, such as\nstress-ng's unlink stressor, producing the following warning:\n\n  WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8\n  Call trace:\n   drop_nlink+0x4c/0xc8\n   v9fs_remove+0x1e0/0x250 [9p]\n   v9fs_vfs_unlink+0x20/0x38 [9p]\n   vfs_unlink+0x13c/0x258\n   ...\n\nIn cacheless mode the server is authoritative and the inode is on its\nway out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count()\nentirely when neither CACHE_META nor CACHE_LOOSE is set, which both\navoids the warning and removes a class of nlink races (two concurrent\nunlinkers observing nlink > 0 and both calling drop_nlink()) that an\nnlink == 0 guard alone would only narrow rather than close."}],"providerMetadata":{"dateUpdated":"2026-08-15T05:53:36.332Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/a5a682b016ef5b5384e28f6d652d47a8f8e73d37"},{"url":"https://git.kernel.org/stable/c/de79c3f3643841b8659a71958df7cf2a66bfd409"},{"url":"https://git.kernel.org/stable/c/8d610017c992de705b304d3d727a6e3a86af6149"},{"url":"https://git.kernel.org/stable/c/8faccac11e1369adddf5d80f4a45af93f13b2e1a"},{"url":"https://git.kernel.org/stable/c/574aa0b4799470ac814479f1138d19efe6262255"}],"title":"9p: skip nlink update in cacheless mode to fix WARN_ON","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-72170","datePublished":"2026-08-15T05:53:36.332Z","dateReserved":"2026-08-09T03:40:39.910Z","dateUpdated":"2026-08-15T05:53:36.332Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-15 06:21:35","lastModifiedDate":"2026-08-15 06:21:35","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"72170","Ordinal":"1","Title":"9p: skip nlink update in cacheless mode to fix WARN_ON","CVE":"CVE-2026-72170","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"72170","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: skip nlink update in cacheless mode to fix WARN_ON\n\nv9fs_dec_count() unconditionally calls drop_nlink() on regular files,\neven when the inode's nlink is already zero. In cacheless mode the\nclient refetches inode metadata from the server (the source of truth)\non every operation, so by the time v9fs_remove() returns, the locally\ncached nlink may already reflect the post-unlink value:\n\n  1. Client initiates unlink, server processes it and sets nlink to 0\n  2. Client refetches inode metadata (nlink=0) before unlink returns\n  3. Client's v9fs_remove() completes successfully\n  4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0\n\nThis race is easily triggered under heavy unlink workloads, such as\nstress-ng's unlink stressor, producing the following warning:\n\n  WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8\n  Call trace:\n   drop_nlink+0x4c/0xc8\n   v9fs_remove+0x1e0/0x250 [9p]\n   v9fs_vfs_unlink+0x20/0x38 [9p]\n   vfs_unlink+0x13c/0x258\n   ...\n\nIn cacheless mode the server is authoritative and the inode is on its\nway out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count()\nentirely when neither CACHE_META nor CACHE_LOOSE is set, which both\navoids the warning and removes a class of nlink races (two concurrent\nunlinkers observing nlink > 0 and both calling drop_nlink()) that an\nnlink == 0 guard alone would only narrow rather than close.","Type":"Description","Title":"9p: skip nlink update in cacheless mode to fix WARN_ON"}]}}}